1. Field of the Invention
The present invention relates to patient interface devices for transporting a gas to and/or from an airway of a user, and, in particular, to a patient interface device including a cam wheel adjustment mechanism for dynamically adjusting a component of the patient interface device, such as a mask, cushion, or forehead support.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), or congestive heart failure.
Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device including a mask component on the face of a patient. The mask component may be, without limitation, a nasal mask that covers the patient's nose, a nasal cushion having nasal prongs that are received within the patient's nares, a nasal/oral mask that covers the nose and mouth, or a full face mask that covers the patient's face. The patient interface device interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient's head.
Because such patient interface devices are typically worn for an extended period of time, it is important for the headgear to maintain the mask component of the device in a tight enough seal against the patient's face without discomfort. A number of different adjustment mechanisms for adjusting a component, such as a mask, of a patient interface device are known, including adjustment mechanisms that are based on sliding members, screw mechanisms, and pivoting arms, among others. However, all of these known mechanisms are based on a linear adjustment theory, and thus have a range of motion that goes either inward or outward with respect to the patient's face. There is thus room for improvement in the area of patient interface device adjustment mechanisms.